Abstract
The N-terminal acetyltransferase A (NatA) complex, which is composed of NAA10 and NAA15, catalyzes N-terminal acetylation of many proteins in a co-translational manner. Structurally, the catalytic subunit NAA10 was believed to have no activity toward an internal lysine residue because the gate of its catalytic pocket is too narrow. However, several studies have demonstrated that the monomeric NAA10 can acetylate the internal lysine residues of several substrates including hypoxia-inducible factor 1α (HIF-1α). How NAA10 acetylates lysine residues has been an unsolved question. We here found that human FIH (factor inhibiting HIF) hydroxylates human NAA10 at W38 oxygen-dependently and this permits NAA10 to express the lysyl-acetyltransferase activity. The hydroxylated W38 forms a new hydrogen-bond with A67 and widens the gate at the catalytic pocket, which allows the entrance of a lysine residue to the site. Since the FIH-dependent hydroxylation of NAA10 occurs oxygen-dependently, NAA10 acetylates HIF-1α under normoxia but does not under hypoxia. Consequently, the acetylation promotes the pVHL binding to HIF-1α, and in turn HIF-1α is destructed via the ubiquitin-proteasome system. This study provides a novel oxygen-sensing process that determines the substrate specificity of NAA10 depending on an ambient oxygen tension.
Highlights
Protein acetylation plays critical roles in many cellular processes including transcription, protein stability, chromatin remodeling, and metabolism [1]
After NAA10 was pre-incubated with Factor Inhibiting HIF (FIH), it catalyzed the acetylation of oxygen dependent degradation domain (ODDD), whereas the W38F mutant did not even after FIH reaction (Fig. 4B). These findings strongly indicate that the FIH-mediated W38-hydroxylation of NAA10 is an essential prerequisite for the lysyl acetylation of hypoxia-inducible factor-1α (HIF-1α) ODDD
Since the HIF-1α K532-acetylation by NAA10 is known to enhance the pVHL binding to HIF-1α [7], we examined whether FIH promotes this interaction through NAA10 W38-hydroxylation in HEK293 and a human breast cancer cell line MDA-MB-231, which was used as a representative cancer cell
Summary
Protein acetylation plays critical roles in many cellular processes including transcription, protein stability, chromatin remodeling, and metabolism [1]. The NAA10-dependent lysine acetylation has been shown in diverse proteins, the argument of this NAA10 activity has been challenged by several reports showing that the HIF-1α acetylation was not reproducible in vitro [5,13,14,15]. To understand such conflicting findings, Seo et al searched for post-translational modifications of human NAA10 using MASS analysis, and found that NAA10 is lysylacetylated by itself and this autoacetylation is critical for the NAA10. The lysyl acetylation facilitates the E3 ubiquitin ligase pVHL to target HIF-1α for degradation under normoxia This scenario may be a reasonable answer to the question about how monomeric NAA10 has the oxygen-dependent activity of lysine acetyltransferase
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